The Original "Bead-On-A-Block"
Standard Bradley - Places the front sight bead on a block of steel for positive indexing, greater surface area and increased strength. Available in red and white colored plastic or gold brass beads. Metric Bradley - Beads are all white in color. Solid Brass Bradley - Uniform yellow brass (gold) or white brass (silver) beads with or without positive-stop skirts.
Big Book Catalog, Issue:70, Page:288
SPECS: Standard Base - steel, blue. Bead - Plastic, red or
white. Brass Beads - gold or silver.